Fluid control system

ABSTRACT

THE CONTROLLER ELEMENT OF A FLUID CONTROL SYSTEM IS A FLUID AMPLIFIER CIRCUIT WHICH SUPPLIES A FLUID FORCE TO AN ACTUATOR ELEMENT FOR RESTORING A SYSTEM PARAMETER TO ITS DESIRED VALUE. A TRANSDUCER SENSES THE SYSTEM PARAMETER AND CONVERTS IT TO A PULSATING FLOW OF CONTROL FLUID OF FREQUENCY PROPORTIONAL TO MAGNITUDE OF THE SYSTEM PARAMETER. FIRST AND SECOND TUNED RESONANT DEVICE, SUCH AS TUNED CAVITIES, CONNECTED TO THE OUTPUT OF THE TRANSDUCER HAVE RESONANT FREQUENCIES RESPECTIVELY ABOVE AND BELOW A FREQUENCY CORRESPONDING TO THE DESIRED VALUE OF THE SYSTEM PARAMETER. THE OUTPUT FLUID FLOWS OF THE FIRST AND SECOND TUNED RESONANT DEVICES ARE SUPPLIED TO THE CONTROL NOZZLES OF THE FLUID AMPLIFIER AND HAVE MAGNITUDES OF FLOW RESPECTIVELY PROPORTIONAL TO THE DEVIATION OF THE SYSTEM PARAMETER ABOVE AND BELOW THE DESIRED VALUE.

May 9, 1972 H. STERN FLUID CONTROL SYSTEM Original Filed May 28, 1963 /27 Ve/vzor.' Hans/ H/ls A orney.

. Int. cl. F151; 13/0-2., l

U.S. Cl. v91-3 v y n 1 Claim Matter enclosed in heavy brackets appears in the original patent but forms no partof this reissue specification; matter printed in italics indicates the additions made by reissue.`

ABSTRACT F THE DISCLOSURE :The controller element of a fiuid control system is a fluid amplier circuit which supplies a fluid force to an actuator elementfor restoring a system parameter to its desired value. A transducer senses the system parameter and converts it to a pulsating flow of control fluid of frequency proportional to Vmagnitude of the system parameter. First and fsecond tuned resonant devices, such as tuned cavities, connected to the output of the transducer have resonant, frequencies respectively above and below a frequency corresponding .to the desired value of the system parameter. The output fluid flows of the first and second tuned resonant devices are supplied to the control nozzles of the fluid amplifier and have magnitudes of flow respectively proportional to the deviation of the system parameter above and below the desired value.

'This is a reissue application for my U.S. Pat. No. 3,233,522 F luid Control System,l filed May 28, 1963 and issued l'feb.` 8, '1966. Y 'j A VMy invention relates to afluid control system employing a fluid amplifier circuit as part ofthe controller element, and in particular, to the portion of the system which generates the control fluid flow utilized` by the fluid amplifier.` ,Fluid amplifier devices are va recent development currently' finding application as digital and analog computing elements. However, their application in more complex fluid control systems has found limited use due primarily to their newness. These devices feature inherent reliability, since they generally employ no moving parts, ease of fabrication, and temperature insensitivity. The devices willope'rate both on incompressible fluids such as liquids 'and eompressible fluids such as gases, including' air, it being understoodthat the material comprising the fluid 'amplifier be compatible with the fluid passing therethrough. As a result, they areA ideal for applications where nuclearyradiation, high temperature, vibration, and shock may be present.

Fluid amplifiers operate on the basis of deflecting a Huid power jet. In the conventional form, a constant main fluid flow comprising a relatively high pressure power jet issues from a nozzle and impinges upon at least' one of two fluid flow receivers. A deflection or control of the power jet is obtained by imparting sideways momentum thereto by means'of control fluid flow comprising relatively'low pressure control jets issuing from -a pair of control nozzles positioned in opposing relationship to the power jet and directed laterally thereto. The magnitilde of power 'jet deflection is proportional V'to the net sideways momentum imparted by the control jets in the class of fluid amplifiers generally known as theranalog type. Deflection of the power jet results in one receiver obtaining more ow or recovering a higher pressure while the other receiver obtains or recovers less. Since the United Sme Pm@ Re. 27,352 Reissued May 9, 1972 v*ice deflection; is proportional, the output flow or pressure at thereceivers is proportional to the net input flow or pressure'at the control nozzles. v

Fluid control systems are useful for controlling th rotational speed of apparatus such as turbines, engines, or hydraulic motors. A particular problem with prior fluid controlsystems of this type has fbeen the factor of reliability. The prior' systems generally employ many moving parts which are sensitive to vibration and thereby subject to erratic behavior or breakdown.

Therefore, one of the principal objects of my invention is to provide a fluid control system employing a fluid amplifier circuit as part of the controller element whereby the system has relatively few moving parts and resultant improved reliability.

Various system conditions or parameters are often required to be controlled in the more complex apparatus of present day technology. These parameters may include rotational speed, frequency, pressure, temperature, and particular functions of a plurality of such parameters.

Therefore, another important object of my invention is to provide a uid control system employing a fluid amplifier circuit wherein the system is adapted to control a specific parameter or a particular function of a plurality of system parameters.

Briefly stated, and in accordance with my invention, I provide a fluid control system wherein a fluid amplifier circuit comprises the controller element. 'I'he fluid amplifier supplies a fluid force to an actuator element for restoring a particular system parameter to a desired value in response to a deviation therefrom. The amplifier is made responsive to the parameter deviation by means of two fluid impedances having impedance values |which vary with the frequency or pulsation of control fluid flow. A first of such impedances resonates at a frequency below a particular frequency which represents the desired value of the system parameter to be controlled, and the second impedance resonates above such particular frequency. The two impedances are employed, respectively, in two control fluid passages of the amplifier whereby the magnitude of each pulsating control fluid flow is determined by the proximity of the control fluid flow frequency to the impedance resonant frequency. Suitable transducers are provided at the input to the impedances to convert the system parameter to a pulsating fluid flow having a frequency which is proportional to the magnitude of the system parameter. Thus, a deviation of the system parameter from its desired value results in an unbalanced control fluid flow to the amplifier, therebey deflecting the power jet in such direction as to restore the system to the desired condition.

The features of my invention which I desire to protect herein are pointed 'out with particularity in the appended claim. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may'best to understood by reference to the following description taken in connection with the acompanying drawings, wherein like parts-'in each of the severall figures are identified by the same reference charcter, and wherein:

FIGURE 1 is a diagrammatic view, partly lin section,

. illustrating a fluid control system for controlling rotain FIGURE '17; and

FIGURE 3 is a graphical' representation of the force applied to theservo actuator illustrated in FIGURE 1V as a function of the frequency characteristics of the two' tuned cavities.

3 Inthe fluid control system illustrated in FIGURE-.'11,v

there is shown a fluid amplifier designated as a whole by numeral 1 and comprising a source of fluid under pressure which is introduced into fluid passage 2 as indicated by the arrow. A-main or power fluid passage 3 may be an extension of passage 2 and terminates in a fluid lflow restrictor forming a nozzle 4 adapted to generate a main Jr power jet of fluid issuing therefrom. Two fluid pasiages 5 and 6, having a smaller cross section than main luid passage 3, branch from passage 2 and convey the luid. which ultimately passes through control iiuid passages 7 and 8. Passages 7 and 8 terminate in fluid flow festrictors forming control nozzles 9 and 10, respectivey, which are adapted to generate control jets of fluid ssuing therefrom. Control nozzles 9 and 10 are posiyioned adjacent power nozzle 4 and disposed on opposite :ides of the power jet and substantially perpendicular hereto whereby each control jet is directed against an )pposite side of the power jet in momentum exchange 'elation. A pair of fluid receiving passages 11 and 12 are lisposed downstream from power nozzle 4 in a manner vhereby in the presence of equal or balanced control ets issuing from nozzles 9 and '10, the non-deflected pow- :r jet is directed midway between receivers 11 and 12. lhe receivers may be spaced apart and the non-deflected :ower jet is either distributed equally between receivers l1 and 12 or passes entirely therebetween. Receivers l1 and 12 are connected to fluid passages 13 and 14, reltpectively, the latter passages being connected, respecively, to opposite ends or sides of a suitable servo actuaor 15 which may be of the hydraulic or pneumatic type ts determined by the fluid medium employed in amplifier l. Actuator. 15 is operable during an unbalanced con- `rol jet condition which causes a deflection of the power et in a manner to be discussed in greater detail hereintfter.

It should be understood that the illustration of fluid tmplifier 1 in FIGURE l is merely a diagrammatic repesentation. The actual construction of a conventional luid amplifier device comprises a base member having a slotted surface which forms the configuration lof the various flow paths such as fluid flow passages 3, 7, 8, l3, 14; nozzles 4, 9, 10; and receivers 11, 12. A cover nember encloses the ow paths to form a sealed device.

A pair of fluid impedances 16, 17 having impedance values which vary with the frequency or pulsation of fluid lowing thereby are connected to the input of control luid passages 7 and 8, respectively. Such impedances are areferably of the resonant type, each resonating at a different predetermined frequency as further described herenafter. The impedances may comprise hollow members 3f suitable size, that is, tuned cavities 16, 17, such as Lhe well-known Helmoltz resonators or organ pipes. Fwo identical transducers 18 and 19 of a type appropriate `:o convert the system parameter to be controlled to a Julsating fluid flow are connected between the outputs )f fluid passages 5 and 6 and the inputs to tuned cavities l6 and 17, respectively. The particular system parameter :o be controlled in the embodiment illustrated in FIG- URE 1 is rotational speed of shaft 20,. Thus, for the :articular application, transducers 18, 19.may convenienty be devices known as choppers which are mounted on :haft 20 and comprise lstructures having fluid passages Jassing therethrough. The constant fluid flow from pas- ;ages Sand 6 thus passes through transducers18 and 19, 'espectively, wherein such flow is V'converted to a pulsatng fluid flow having a frequency of pulsation proportionrl'to the rotational speed of shaft 20. The pulsating fluid lowl exits from the transducers and enters tuned cavities l6 and y1 7 which have frequency resonance characteristics illustrated in FIGURE 2.'Suitable bearings 21, 22 are provided on shaft 20 for supporting the transducers. Suitable fluid means are provided at the output of tuned :avities 16 and 17 to obtain a function'analogous to rectifyingraction in electrical circuits-to eliminate back flow of the control fluid.

The system illustrated in FIGURE 1 represents a speed governor control wherein the rotational speed of shaft 20 which may be driven by a turbine, engine, or hydraulic or pneumatic motor is to be controlledV or maintained at a desired speed. The control system functions in the following manner. Tuned cavities 16 and 17 are adapted to resonate, respectively, at w1, a frequency-below w, and wz, a frequency above w wherein w is a desired frequency to be controlled and is proportional to the desired rotational speed ofv shaft 20. The frequencies lare in a range between 50 c.p.s. and 10 k.c.p.s..the frequency spread between w1 andwz being preferably approximately 20 percent of w. A smallflow off-fluid from passages 5 and 6 is metered into cavities 16, 17 through choppers 18, 19. At shaft rotational speed below that desired to be maintained the pulsating fluid flow generated by the transducers has a frequency below w and thus closer to the resonance frequency w1 of cavity 16 than wz of cavity 17. Thus, tuned cavity 16 supplies a'larger control fluid flow to pasage 7 than that provided by cavity 17 to passage 8. Such unequal control fluid flow in passages '7` and 8 produces an unequal or unbalanced control jet effect which deflects the power jet issuing from nozzle 4 toward receiver 12 and'ther'eby produces a positive forcev to operate servo actuator 15 as illustrated in FIGURE 3 which is in a direction to increase thefshaft speed. Actuator 15 is connected to suitable'valves, throttle or stroke mechanism of the energizing portion of the appara.- tus which drives or rotates shaft 20. At speeds above the desired speed, tuned cavity 17 suppliesa larger control lluid flow to passages, thereby correcting the speed of shaft 20 in the opposite direction. At thedesired shaft speed, the frequency of Athe pulsating fluid flow generated by the transducers isA w, and the control fluid flows through passages 7 and 8 are in balance and no net deflection of the power jet results. Thus, it4 can be appreciated that myfluid control system is adapted to maintain a desired rotational speed of shaft 20 and a deviation from this desired condition produces an error signal, that is, unbalanced control fluid flows which restore the system to the desired condition of shaftfspeed.

In jet engines the function where N is the rotational 'speed of the jet engine and '0 is corrected jet engine temperature, is a system parameter which is controlled to maintainjet engine top corrected speed. A gas is preferably employed as the working fluid in my control system for controlling this particular system parameter since ythe resonant frequency of the tuned cavities 16, 17 vary as V0 for a gaseous fluid. Thus, the system illustrated in FIGURE 1 may be employed in a high temperature application such as a gas turbine j et engine control to regulate top speed without the need for complicated temperature sensors. If hydraulic fluids are used for the working medium, their compressibility is valso a function'of temperature and the cavity resonance will thus also be temperature dependent. Over certain ranges of temperature, a thermal compensatoi' can be introduced in the tuningcavities if resonance is to be independent of temperature". l,

` Having' described a new iluidvcontrolsystem employing a fluid amplifier as part ofthecontrolling element,.it is believed obvious that vmodifications-,and variations' of my invention are possible in the light of the above teachings...Th us, a variety of: system parameters'may be controllerd `such as linear velocity, pressure, temperature, and anyother parameter for which asuitabletranSduCer is available to convert Suchparameter to a' pulsating flow having a frequency of pulsation proportional to the magnitude of thegsystem parameter. some cases, it maybe ,convenient to employ a single fluid Ipassage branching from passage ,Zand a single trnsducerhaving',

two outputs connected to cavities 16 and 11. Althoughthe sp'eedg'overnor control illustrated in FIGURE I1 employs two identical transducers, fthereare applications -wherein nonidentical transducers are utilized, such asin a system whichregulates a Vratio betweenV two ldifferent' speeds.

`It is, therefore, to be understood that changes may be `made in the particular embodiment of my inrvention described which are within the full intended scope of the invention as defined by the following claim.

What I claim as new and desire to secure by I etters Patent of the United States is:

i [1. A fluid control systemfor maintaining a desired value of a selectedsystem parameter comprisinga fluid amplifier ycomprising a first 'fluid passage terminating in a first fluid flow restrictor for generating a main fluid jet to be controlled, a pair of [fluid receiver means downstream from said first restrictor for receiving fluid from the main jet, and a pair of second fluid passages terminating in oppositely disposed second fluid flow restrictors for generating l control fluid jets to 4controllably deflect the main gjet relative to said receiver means,

first means in fluid communication with the input to a first of said second fluid passages for generating a first pulsating vflow of control fluid having a magnitude of flow responsive to deviations of said system ,f parameter above the desired value, vsecond means in fluid communication with the input to asecond of saidrsecond fluid passages for generating a second pulsating flow of control fluid having a magnitude of 4flow responsive to deviations of said system parameter below the desired value, and means in fluid communication with said receiver l means for restoring lsaid system parameter to the desired value] [2. A fluidi control system for maintaining a desired value of a particular system parameter comprising- 'a uid amplifier comprising a -first fluid passage terminating in a first noule for generating a power jet yof .fluid to be controlled, a pair of fluid receiver means downstream from said first nozzle for receiving fluidfrom the power jet, and a pair of second *fluid passages terminating in a pair of oppositely disposed second nozzles for generating jets of control fluid,v to controllably deflect the power jet relative to lsaid receiver means, ifirst means for generating la pulsating flow of said control fluid whereinthe frequency of pulsation is proportional to the magnitude of said system parameter, r second means for-controlling the magnitude of said pulsating control fluid flow, 'said second means comprising Va Afirst frequency sensitive fluid impedance responsive to deviations of said system parameter above the desired value, the output of said first V impedance being connected to the input of a first of said second fluid passage, and a second frequency ysensitive fluid impedance responsive to deviations of said system parameter below the desired value, the loutput of said second impedance being connected to the input of a second of said second fluid passages, andv means in fluid communication lwtih said receivermeans for restoring said `system parameter to the desired Y value] [3. A fluid control system Ifor maintaining a desired magnitude of a particular system parameter comprisinga Ifluid amplifier comprising a first fluid passage terf minating in a first nozzle for generating a power jet of fluid to be controlled, a pair of fluid receiver means downstream from said first nozzle for receiving fluid from the power jet, and a pair of -second fluid passages terminating in a pair of oppositely disposedsecond nozzles for generating jets of con "trol fluid Yto controllably deflect the power jet relative y. to said receiver means,

means for generating a pulsating'flow o f said control U 'fluid `wherein the frequency of pulsation is propor- A tional tothe magnitude of the systempara-rneter, `a first fluid impedance resonantlata frequency above a selectedl frequency, said selected frequency rep-V resenting the desired magnitude of the system parameter,

a second fluid impedance resonant at a frequency below said selected frequency, the input to said first and second fluid impedance being connected to the output of said pulsating control fluid generating means, the output of said first and second fluid impedance being connected respectively to an input of a first `and second of said second fluid passages whereby said jets of control fluid have magnitudes of control fluid flow determined by deviation of the frequency of pulsation of control fluid flow from said selected frequency, and

ymeans in fluid communication with said receiver means for restoring said system parameter to the desired magnitude] [4. A speed control system for maintaining a desired speed comprisinga fluid amplifier comprising a first fluid passage terminating-in a first fluid flow restrictor for generating a main fluid jet to be controlled, a pair of fluid receiver means downstream from said first restrictor for receiving fluid from the main jet, and a pair of second -fluid passages terminating in a pair of oppositely disposed second fluid flow restrictors for generating a pair of opposing control fluid jets to controllably deflect the main jet relative to said receiver means,

transducer means for generating a pulsating flow of the control fluid wherein the frequency of pulsation is proportional to the system speed,

a first tuned cavity connected to an output of said transducer means, said first cavity having a resonant frequency corresponding to a particular speed above the desired system speed, the output of said first tuned cavity being connected to an input of a first of said second fluid passages,

a second tuned cavity connected to an output of said transducer means, said second cavity having a resonant frequency corresponding to a particular speed Ibelow the desired system speed, the output of said second tuned cavity being connected to an input of a second of said second fluid passages, and

means responsive to a deflection of said main fluid jet resulting from an unbalanced condition of the control nid jets for adjusting the system speed to the desired speed at which t-he control jets are in a bailanced condition] :[5. A speed control system for controlling a desired rotational speed comprisinga fluid amplifier comprising a first fluid passage terminating in a first fluid flow restrictor for generating a main fluid jet to be controlled, a pair of fluid receiver means downstream from said first restrictor for receiving fluid from the main jet, and a pair of second fluid passage terminating in a pair of oppositely disposed second fluid flow restrictors for generating a pair of opposing control fluid jets to controllably deflect the main jet relative to said receiver means.

a first transducer means for generating a first pulsating :flow of the control fluid wherein the frequency of pulsation is proportional to the system speed,

a second transducer means for generating a second pulsating flow of the control fluid wherein the frequency of pulsation is proportional to the system speed,

. a first-tuned cavity connected to an ,output of said rst transducer, said rst cavity having a resonant frequency corresponding kto a particular speedl above the desired .system speed, the output of said rst cavity beingconnected to an input of a irst of said i second uid passages whereby a 'first of saidcontrol Vilud jets `is responsive .to deviations of the` system speed above the desired speed,

a second tuned cavity connected to an output of said second transducer, said second cavity having a resonant frequency corresponding to a particular speed below the desired system speed, the output of said second cavity being connected to an input of a second of said second fluid passages whereby a second of said control uid jets is responsive to deviations of the system speed below the desired speed, and

means responsive to a deflection of said main fluid jet for adjusting the system speed to the desired speed at which a balanced condition of said control jets is obtained, said main jet deection resulting from an undesired system speed which renders one of said tuned cavities more responsive and thereby conveys a greater control iluid flow to the said second uid ow restrictor in fluid communicator therewith to produce an unbalanced condition of the control jets] 6. A fluid control system. for controlling a desired system parameter comprising:

27ste a` firs branchiutssage` having 'endend c l f, necte #to .saidmatn power fluidfpassage forlreoeiving y.fluid flow. therefrom .and the.otherenaylocatedin juxtaposed relation'v tv ovlsaid f first transducer mean providing fluid flow theretojv (h)r aV secondtransducerfmeans forgenerating a second pulsating flow of4 thev control fluidvwheren the v'fre-- quencyl of pulsation is proportional Ato' the'syste'm parameter;

` (i) a second tuned cavityupostio'ned in juxtaposed relation to said secondjransducer means forv receiving 'an output directly therefrom, said'second cavity having'a resonant frequency correspondingtaparticular value below the desired system parameter; v l

( j) said second tuned cavity further being positioned in juxtaposed relation to'l the input ofv a second of said pair of second fluid passages 'of saidv fluid amplifier for providing the output of said second tuned cavity directly to said input of said second of said `pair of second fluid passages ofsaid fluid amplifier whereby a second of said control fluid jetsis responsive to deviations of the system parameter below` the desired value;

(k) a second branch passage havingone end directly connected to said main power fluid passage for receiving fluid flow therefrom'and the other end located in juxtaposed relation to said second transducer means for providing fluid flow thereto; and l (l) means responsiveflto'a deflection of s'f'dfmain fluid jet for adjusting the system parameter'tothe desired value at which a balanced condition of'said control jets is obtained, said main jet deflection resultingffrom an undesired systemjh'value which `renders'lone of said tuned cavities moire responsiveand thereby conveys a greater control fluid flowA to th'e saidy second; fluid flow restrictor in fluid communication'therewith to produce an unbalanced condition of the `control jets.

References Cited The following references, cited by tbe iiaminer, are of record in the patented le of this patent or the original means; (c) a main power fluid passage having one end' directly connectable to said source of fluid for receiving fluid 40 therefrom, and the other end directly connected to patent said firJsqt pasage of said fluid amplifier for sup- UNITED ATES-JPATENTS" pymg u1 ere o; s. ti y (d) a first transducer rneans for generating a first puletsal tr-T-v 35g sating flow of thecontrol fluid wherein the frequency 1959889 5/1934 gs cliff"- 7 IgG-X of pulsation is proportional to the system parameter; 2485094 10/1949 Gunc ""7 t 13'783 X l(e) a first tuned cavity positioned in juxtaposed rela- 2727525 12/195517Hunier-s-efn 13; 815 tion to said first transducer means for receiving an 2814487 11/19571-: arr-S 1371155 output directly therefrom, said first cavity having a 2982902 5/1961 'f s g3 X resonant frequency corresponding to a particular value 3144037 8/1964 13,7. 81 5 above the desired system parameter; 3176094 3/1965 Y ff1s371-*36 (f) said first tuned cavity further being positioned in 3193197 7/1965 1-37 5 X juxtaposed relation to the input of a first of said pair f f. l ,t v, of second fluid passages of said fluid amplifier for prot viding the output of said first tuned cavity directly to 55 CARROLL R' DORITY JR" aryixmlill said input of said first of said pair of second fluid Us; C1,X R passages of said fluid amplifier whereby a first of said 137 31 5 f,

control fluid jets is responsive to deviations of the sys tem parameter above the desired value; 

